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Abstract:

An apparatus and method are provided that allow for the realignment and
stabilization of adjacent vertebrae. An implant of this invention both
repositions adjacent vertebrae and remains in situ to maintain the new
position. The implant has two halves which are interlocked such that they
can slide horizontally with respect to each other. Movement of the
implant halves and their respective positions are controlled by set screw
within the implant. The implant includes radial anchors which fit into
alignment slots made in the misaligned vertebra by the disclosed method.
The set screws are used to advance the halves of the implant which in
turn move the misaligned vertebrae back into correct positions. The
correct position of the vertebrae is locked in place through a nut and a
plate.

Claims:

1. A system for correcting alignment between two vertebrae caused by
spondylotisthesis comprising: a distractor having a distractor body with
a hollow chamber along a distractor body longitudinal axis, an anterior
end, a posterior end having first a first longitudinal extension and a
second longitudinal extension which extend from the distractor body in
the direction of the distractor body longitudinal axis, the first
longitudinal extension having a first stop surface perpendicular to the
first longitudinal extension and extending parallel to the distractor
body, the second longitudinal extension having second stop surface
perpendicular to the second longitudinal extension and extending parallel
to the distractor body, a gap between the first stop surface and the
second stop surface, a measurement scale along the first longitudinal
extension, and a torque handle perpendicularly attached to the distractor
body; an impactor having an impactor handle, an impactor body having a
longitudinal axis, a latitudinal axis, an impactor body anterior end, and
an impactor body posterior end, the impactor handle being centered on the
latitudinal axis of the impactor body anterior end, an impactor seat
centered along the latitudinal axis of the impactor body posterior end;
the impactor seat fits within the gap on the distractor; a gate having a
gate longitudinal axis, a gate latitudinal axis, a distractor end and a
guide end, the distractor end having an insertion conduit and having a
distractor stop, the guide end having a guide conduit, a top side, a
bottom side, a right side, a left side, a gate anterior end, a first set
of a guide slots from a first centerline of the right side to a second
centerline of the bottom side and parallel to the gate anterior end, a
second set of guide slots from a third centerline of the left side to a
fourth centerline of the top side and parallel to the gate anterior end,
a first side slot along the first centerline of the right side and
ductedly connected to the first set of guide slots and terminating in a
first end, a second side slot along a second centerline of the left side
and ductedly connected to the second set of guide slots and terminating
in a second end, the first set of guide slots having a first set spacing
and the second set of guide slots having a second set spacing, the first
set spacing related to the second set spacing by a third set spacing; a
saw unit with a saw longitudinal axis, the saw unit having a saw handle
jointed to spindle connected to a saw blade, a saw guide body, and a saw
guide projection, the saw guide projection joined to the handle at an
angle generally perpendicular to the saw longitudinal axis, the saw guide
body further having a longitudinal pivot hole coaxial with the saw
longitudinal axis, the guide body further having a horizontal blade stop
and a vertical blade stop, the spindle rotatively mounted in the
longitudinal pivot hole, the saw blade having a saw blade longitudinal
axis parallel to the saw guide projection and movable between a stoppage
position dictated by the horizontal blade stop and an operational
position dictated by the vertical blade stop; an implant having a first
half having a first body with a longitudinal axis, a first collar, a
first chamber, a first joint, a first longitudinal side and a first set
of radial anchors, the first set of radial anchors radially extending
generally perpendicularly from the first body, a second half having a
second body with a second longitudinal axis, a second collar, a second
chamber, a second joint, a second longitudinal side and a second set of
radial anchors, the second set of radial anchors radially extending
generally perpendicularly from the second body, the first half and the
second half slidably connected by the first joint and the second joint
along the first longitudinal side and the second longitudinal side, the
first body and the second body connected form an implant body, the first
collar and the second collar connected form an implant collar, the first
chamber and the second chamber connected form an implant chamber, the
first chamber being threaded with a first set of threads, a drive screw
having an outside perimeter and a spanner head, the outside perimeter
being threaded with a second set of threads, the drive screw located in
the implant chamber, the first set of threads in engagement with the
second set of threads, the first set of threads and the second set of
threads having a pre-determined relationship to allow the first half to
move a pre-determined distance in relation to the second half when the
drive screw is rotated a pre-determined angle of rotation, the first set
of radial anchors and the second set of radial anchors being generally
parallel, the first set of radial anchors having a first set of corners
and a second set of corners, and the second set of radial anchors having
a third set of corners and a fourth set of corners, an inserter having a
top half and a bottom half, the top half further having a top
longitudinal axis and a top joint along the top longitudinal axis, the
top half having a first semi-cylindrical section and a first
semi-hexagonal section, the bottom half having a bottom longitudinal axis
and a bottom joint along the bottom longitudinal axis, the bottom half
having a second semi-cylindrical section and a second semi-hexagonal
section, the top half and the bottom half slidingly connected along the
top joint and the bottom joint and create a cylindrical section and a
hexagonal section, the top half having a connection end, the connection
end having a threaded connection channel; the threaded connection channel
having a fourth pitch; the third pitch of the collar perimeter matching
the fourth pitch of the threaded connection channel; a guide block having
a guide block longitudinal axis, a top cap connected to an insertion
bottom, and an inserter hole centered through the guide block
longitudinal axis; a nut having a nut head and a nut body, the nut body
being generally perpendicular to the nut head, the nut body having a
threaded implant hole, the threaded implant hole having fifth pitch; the
third pitch of the collar perimeter matching the fifth pitch of the
threaded implant hole; and a plate having a plate hole, a plurality of
screw holes, and a face, a back, and the plate hole having a face
diameter and a back diameter.

2. The system of claim 1 wherein the face diameter is larger than the
back diameter.

3. The system of claim 1 wherein the first implant half further comprises
a first set of alignment marks and the second implant half further
comprises a second set of alignment marks and the first set of alignment
marks when the first set of radial anchors is parallel with the second
set of radial anchors.

4. The system of claim 1 wherein the first stop surface has a first
posterior end and the second stop surface has a second posterior end, and
the first posterior end and the second posterior end are rounded.

5. The system of claim 1 wherein the nut head has a rotational insert,
and the rotation insert has the shape of one of the group of hexagonal,
and spanner.

6. The system of claim 1 wherein the gate has a pointing means for
indicating a gate orientation.

7. The system of claim 1 wherein the measurement scale has a plurality of
markings spaced 1 mm apart.

8. The system of claim 1 wherein the impactor handle has a centerline
which is parallel to a horizontal axis of the impactor body.

9. The system of claim of claim 1 wherein the first longitudinal
extension having a first tapering end and the second longitudinal
extension having a second tapering end, the first tapering end tapering
in height by a set tapering degree, and the second tapering end tapering
in height by the set tapering degree; and the impactor body having a
tapering end, the tapering end tapering in height by the set tapering
degree.

10. The system of claim 1 wherein the saw unit includes a handle housing,
a motor rigidly mounted in the handle housing, a drive shaft extending
from and driven by the motor, the drive shaft extending through a hole in
the handle housing and the spindle, a transmission housing rigidly
attached to the spindle, a transmission located within the transmission
housing, the transmission operatively connected to the drive shaft and to
a chuck; the chuck releasably fixed to a mill bit; the transmission
housing further comprising an index means for limiting the rotation of
the transmission housing with respect to the guide body.

11. A system of tools for inserting an implant for correcting a
spondylotisthesis condition between two affected vertebrae comprising: a
distractor having a distractor body with a hollow chamber along a
distractor body longitudinal axis, an anterior end, a posterior end
having first a first longitudinal extension and a second longitudinal
extension which extend from the distractor body in the direction of the
distractor body longitudinal axis, the first longitudinal extension
having a first stop surface perpendicular to the first longitudinal
extension and extending parallel to the distractor body, the second
longitudinal extension having a second stop surface perpendicular to the
second longitudinal extension and extending parallel to the distractor
body, a gap between the first stop surface and the second stop surface,
and a torque handle attached to the distractor body; an impactor having a
striking end and a posterior end; the impactor fitting within the hollow
chamber of the distractor; a gate with a gate longitudinal axis, a gate
latitudinal axis, a distractor end and a guide end, the distractor end
having an insertion conduit and having a distractor stop, the guide end
having a guide conduit, a first side, a second side, a third side, a
fourth side, a gate anterior end, a first set of a guide slots from
centerline of the fourth side to centerline of the second side and
parallel to the gate anterior end, a second set of guide slots from
centerline of the third side to centerline of the first side and parallel
to the gate anterior end, a third guide slot along centerline of the
fourth side and ductile connected to the first set of guide slots and
terminating in a first end, a fourth guide slot along centerline of the
fourth side and ductile connected to the second set of guide slots and
terminating in a second end, the first set of guide slots having a first
set spacing and the second set of guide slots having a second set
spacing, the first set spacing related to the second set spacing by a
third set spacing; the anterior end of the distractor fitting within the
insertion conduit but not within the guide conduit; a saw unit with a saw
longitudinal axis, the saw unit having a handle joined to a spindle
connected to a saw blade, a saw guide body, and a saw guide projection,
the saw guide projection joined to the handle at an angle perpendicular
to the saw longitudinal axis, the saw guide body further having a
longitudinal pivot hole coaxial with the longitudinal axis, the spindle
rotatively mounted in the longitudinal pivot hole, the saw blade movable
between a stoppage position and an operational position; the saw guide
body fitting within the guide conduit of the gate and the hollow chamber
of the distractor; an implant adapted to be fitted between the affected
vertebrae having a first half having a first half longitudinal axis, a
first half outer surface, and a first joint and a second half having a
second half longitudinal axis, a second half outer surface, and a second
joint, the first half and the second half connected by the first joint
and the second joint forming an implant body, the first half having a
first channel and the second half having a second channel such that when
the first half and the second half are connected the first channel and
the second channel form an implant chamber in the implant body, a drive
bolt located inside the implant chamber having a first set of threads,
the first channel being threaded, a second set of threads, the first half
having a first set of radial anchors extending perpendicularly from the
first half outer surface and the second half having a second set of
radial anchors extending perpendicularly from the second half outer
surface; the first set of threads engaging the second set of threads; an
inserter having a top half and a bottom half, the top half having a top
longitudinal axis and a top joint along the top longitudinal axis, the
bottom half having a bottom longitudinal axis and a bottom joint along
the bottom longitudinal axis, the top half and the bottom half slidingly
connected along the top joint and the bottom joint, the top half having a
connection end, the connection end releasably connectable to the implant
body; a nut having a nut head and a nut body, the nut body being
perpendicular to the nut head, the nut body having an implant hole,
releasably connectable to the implant body; a plate connectable to the
two affected vertebrae having a plate hole through which passes the nut
body.

12. The system of claim 11 wherein the implant body has a set of
alignment marks on the first implant half and the second implant half.

13. The system of claim 11 wherein the gate has a pointing means for
tactically discerning a direction of insertion.

14. The system of claim 11 wherein the distractor has a measurement scale
along the first longitudinal extension.

15. The system of claim 11, where the impactor has an impactor handle, an
impactor body having a longitudinal axis, a latitudinal axis, an impactor
body anterior end, and an impactor body posterior end, the impactor
handle being centered on the latitudinal axis of the impactor body
anterior end, an impactor seat centered along the latitudinal axis of the
impactor body posterior end; the impactor seat fits within the gap on the
distractor.

16. The system of claim 11 where the guide body further having a
horizontal blade stop and a vertical blade stop.

17. The system of claim 11 further comprising a guide block having a
guide block longitudinal axis, a top cap connected to an insertion
bottom, and an inserter hole centered through the guide block
longitudinal axis; the insertion bottom fitting into the hollow chamber.

18. The system of claim 11 further comprising a set of distractors,
wherein each distractor of the set of distractors has a unique height.

19. The system of claim 11 further comprising a set of impactors, wherein
each impactor of the set of impactors has a unique height.

20. The system of claim 11 further comprising a set of saw guide bodies,
wherein each saw guide body of the set of saw guide bodies has a unique
height.

21. The system of claim 11 further comprising a set of implants, each of
the set of implant bodies having a unique diameter.

22. A system of tools for inserting an implant for correcting a
spondylolisthesis condition between two affected vertebrae comprising: a
distractor having a distractor body with a hollow chamber along a
distractor body longitudinal axis, an anterior end, a posterior end
having first a first longitudinal extension and a second longitudinal
extension which extend from the distractor body in the direction of the
distractor body longitudinal axis, the first longitudinal extension
having a first tapering end and a first stop surface perpendicular to the
first longitudinal extension and extending parallel to the distractor
body, the second longitudinal extension having a second tapering end and
a second stop surface perpendicular to the second longitudinal extension
and extending parallel to the distractor body, the first tapering end and
the second tapering end tapering in height by a set tapering degree; a
gap between the first stop surface and the second stop surface, and a
torque handle attached to the distractor body; an impactor having a
striking end, a posterior end, and an impactor body, the impactor body
having a tapering end, the tapering end tapering in height by the set
tapering degree; the impactor fitting within the hollow chamber of the
distractor; a gate with a gate longitudinal axis, a gate latitudinal
axis, a distractor end and a guide end, the distractor end having an
insertion conduit and having a distractor stop, the guide end having a
guide conduit, a first side, a second side, a third side, a fourth side,
a gate anterior end, a first set of a guide slots from centerline of the
fourth side to centerline of the second side and parallel to the gate
anterior end, a second set of guide slots from centerline of the third
side to centerline of the first side and parallel to the gate anterior
end, a third guide slot along centerline of the fourth side and ductedly
connected to the first set of guide slots and terminating in a first end,
a fourth guide slot along centerline of the fourth side and ductedly
connected to the second set of guide slots and terminating in a second
end, the first set of guide slots having a first set spacing and the
second set of guide slots having a second set spacing, the first set
spacing related to the second set spacing by a third set spacing; the
anterior end of the distractor fitting within the insertion conduit but
not within the guide conduit; a saw unit with a saw longitudinal axis,
the saw unit having a handle joined to a spindle, the handle having a
handle housing, a motor rigidly mounted in the handle housing, a drive
shaft connected to and driven by the motor, the drive shaft extending
through a hole in the handle housing and the spindle, a saw guide
projection joined to the handle at an angle perpendicular to the saw
longitudinal axis, the saw guide body further having a longitudinal pivot
hole coaxial with the longitudinal axis, the spindle rotatively mounted
in the longitudinal pivot hole, a transmission housing rigidly attached
to the spindle; a transmission located within the transmission housing,
the transmission operatively connected to the drive shaft and to a chuck;
the chuck releasably fixed to a mill bit; the transmission housing
further comprising an index means for limiting the rotation of the
transmission housing with respect to the guide body, the mill bit movable
between a stoppage position and an operational position; the saw guide
body fitting within the guide conduit of the gate and the hollow chamber
of the distractor; an implant adapted to be fitted between the two
affected vertebrae having a first half having a first half longitudinal
axis, a first half outer surface, and a first joint and a second half
having a second half longitudinal axis, a second half outer surface, and
a second joint, the first half and the second half connected by the first
joint and the second joint forming an implant body, the implant body
further having a front cross-section and a back cross-section, the front
cross-section being generally circular and the back cross-section being
generally circular; the front cross-section connected to the back
cross-section by a generally cylindrical surface with a taper; the taper
having a set incline, the first half having a first channel and the
second half having a second channel such that when the first half and the
second half are connected the first channel and the second channel form
an implant chamber in the implant body, a drive bolt located inside the
implant chamber having a first set of threads, the first channel being
threaded, a second set of threads, the first half having a first set of
radial anchors extending substantially perpendicularly from the first
half outer surface and the second half having a second set of radial
anchors extending substantially perpendicularly from the second half
outer surface; the first set of threads engaging the second set of
threads; an inserter having a top half and a bottom half, the top half
having a top longitudinal axis and a top joint along the top longitudinal
axis, the bottom half having a bottom longitudinal axis and a bottom
joint along the bottom longitudinal axis, the top half and the bottom
half slidingly connected along the top joint and the bottom joint, the
top half having a connection end, the connection end releasably
connectable to the implant body; a nut having a nut head and a nut body,
the nut body being perpendicular to the nut head, the nut body having an
implant hole, releasably connectable to the implant body; a plate
connectable to the two affected vertebrae having a plate hole through
which passes the nut body.

23. The system of claim 22 wherein the implant body further comprises a
set of indexing marks on the first implant half and the second implant
half.

24. The system of claim 22 wherein the gate further comprises a pointing
means for tactically discerning a direction of insertion.

25. The system of claim 22 wherein the distractor further comprises a
measurement scale along the first longitudinal extension.

26. The system of claim 22 where the guide body further comprising a
horizontal blade stop and a vertical blade stop.

27. The system of claim 22 further comprising a set of gates wherein each
gate in the set of gates has a different third set spacing.

28. The system of claim 22 further comprising a set of distractors,
wherein each distractor of the set of distractors has a unique height.

29. The system of claim 22 further comprising a set of impactors, wherein
each impactor of the set of impactors has a unique height.

30. The system of claim 22 further comprising a set of saw guide bodies,
wherein each saw guide body of the set of saw guide bodies has a unique
height.

31. The system of claim 22 further comprising a set of implants, each of
the set of implant bodies having a unique diameter.

[0002] The present inventions relates generally to the correction of
spondylolisthesis and other spinal column injuries or deformities in the
fields of neurosurgery and orthopedics. More specifically, the invention
is used for the stabilization of repositioned vertebral bodies.

BACKGROUND OF THE INVENTION

[0003] Spondylolisthesis is a medical condition in which one vertebra
slips forward in relation to an adjacent vertebra usually in the lumbar
region of the spine. This condition can cause symptoms that include pain
in the low back, thighs, and/or legs, muscle spasms, weakness, and/or
tight hamstring muscles while in some cases only radiographic imaging
reveals the condition.

[0004] To correct this condition and other similar conditions of vertebral
dislocation, the only effective long-term curative treatment is
reconstructive surgery and fusion of the affected vertebra to its
adjacent neighbor. Vertebral fusion is generally accomplished by fixing
apparatus to and between vertebrae. In addition to the stabilization and
correction of spondylolisthesis, other spinal conditions may be:
stabilization of fractures, correction of spinal deformities (e.g.
scoliosis, kyphosis), stabilization and correction of degenerative spinal
lesions and narrow spinal canal, reconstruction after tumor resection,
and secondary spinal surgery.

[0005] The novel method and implant discussed herein allows for the
correction of spondylolisthesis by movement of the vertebrae into better
alignment while maintaining stabilization of the vertebrae in the new
position in order for the spinal fusion to be completed by ossification.
Specifically, the implant is used to move the vertebrae into a
post-surgical position and keep the vertebrae in the post-surgical
position during the ossification process.

[0006] Roggenbuck in U.S. Pat. No. 6,491,695 discloses the use of an
apparatus and method for aligning vertebrae which involves creating a
helical threaded surface in endcaps of the vertebrae and then threading a
positioning device into position to align the vertebrae. Once the
vertebrae are positioned, the positioning device is removed and an
implant is inserted to maintain the vertebrae in position.

[0007] Ray in U.S. Pat. No. 6,582,431 discloses the use of an expandable
non-threaded spinal fusion device which requires the vertebrae to be
moved into correct position before the device can be inserted and
implanted.

[0008] Betz in U.S. Pat. No. 6,533,791 discloses a device for
stabilization of the lumbar spinal column which requires cutting helical
thread marks into the vertebrae that are to be repositioned and then
installing an implant to maintain the position. The repositioning device
does not stay in the body after the surgery but instead an implant must
be inserted to maintain the repositioning.

[0009] Therefore, there is a need in the art to combine an implant with a
repositioning device in order to reduce the possible repositioning of the
vertebrae. There is a further need in the art to provide for adjustment
of the vertebrae after an implant has been installed.

SUMMARY OF INVENTION

[0010] Disclosed is an apparatus and method for aligning vertebrae due to
slippage of the vertebrae relative to each other. To this end, a method
and apparatus is disclosed for placing a novel implant between two
vertebrae which will move the vertebrae into proper alignment and
maintain that alignment until ossification can occur. The implant
disclosed is left in situ once the vertebrae have been repositioned. The
implant disclosed also provides support for the effected vertebrae
superior to that of previous methods known in the prior art. The implant
also allows for fine adjustments and post implantation adjustments of the
vertebrae superior to that of the prior art.

[0011] The disclosed method includes approaching the vertebra anteriorly
and removing a portion of vertebral disk between the misaligned
vertebrae. Known interbody spacers are then inserted between the
vertebrae until the proper restorative height is achieved. The spacers
are removed and a distractor is placed between the vertebrae in order to
guide the subsequent placement of the implant. A novel gate is inserted
over a novel distractor to properly guide a novel saw mechanism to cut
into the vertebrae at precise locations and allow for the insertion of a
novel implant. Different gates are provided depending on the necessary
restorative height to be achieved and amount of slip between the
vertebrae.

[0012] The disclosed implant has two halves which include a dovetail
groove system which locks the two halves together but allows them to
slide with respect to each other along their longitudinal axis. The
implant has radial anchors which extend from each half and which fit into
slots in the vertebrae cut by the saw. The implant includes a drive bolt
which engages the two halves and which, when turned, slides one half of
the implant in relation to the other. The advancing halves of the implant
carry the radial anchors with them that align the vertebrae. Depending on
the amount of slip between the vertebrae and the necessary restorative
height, different sized implants and associated tools may be used.

[0013] The implant is inserted through a distractor by use of an inserter.
The halves of the implant are aligned so that the radial anchors
correspond to slots made in the misaligned vertebrae. The implant is
rotated into place by the inserter such that the radial anchors fit
securely in the slots previously made by the saw in the vertebrae. The
distractor is then removed.

[0014] In the case of anterior listhesis of the superior vertebra, the
drive bolt of the implant is then rotated so that the upper half of the
implant is advanced posteriorly. The superior vertebra is pulled
posteriorly with respect to the inferior vertebra by the movement of the
upper half of the implant with respect to the lower half.

[0015] The position of the implant is locked into place by use of an
articulating combination of a nut and a plate, thereby maintaining
alignment of the vertebrae. The nut and plate can be removed, allowing
for post-surgical adjustment of the implant.

BRIEF DESCRIPTION OF DRAWINGS

[0016] The disclosed inventions will be described with reference to the
accompanying drawings, which show important sample embodiments of the
invention and which are incorporated in the specification hereof by
reference, wherein:

[0017] FIG. 1 is a side view of a section of human spine characterized by
a spondylolisthesis condition.

[0018] FIG. 2 is an isometric view of a distractor of a preferred
embodiment of the invention.

[0019] FIG. 3a is an isometric view of an impactor of a preferred
embodiment of the invention.

[0020] FIG. 3b is an isometric view of an impactor in conjunction with a
distractor of a preferred embodiment of the invention.

[0021] FIG. 4 is a side view of a section of a human spine with the
distractor in place between vertebrae.

[0022] FIG. 5a is a partial isometric view of a gate of a preferred
embodiment of the invention.

[0023] FIG. 5b is a plan view of a gate of a preferred embodiment of the
invention.

[0024] FIG. 5c is an elevated view of a gate of a preferred embodiment of
the invention.

[0025] FIG. 6 is an exploded isometric view of a saw of a preferred
embodiment of the invention.

[0026] FIG. 7a is a partial plan view of the relational section of the saw
of a preferred embodiment of the invention.

[0027] FIG. 7b is a partial isometric view of the spindle shaft of a
preferred embodiment of the invention.

[0028] FIG. 7c is a partial side view of the spindle shaft of a preferred
embodiment of the invention.

[0029] FIG. 8a is an end view of the saw with the saw blade in a lowered
position of a preferred embodiment of the invention.

[0030] FIG. 8b is an end view of the saw with the saw blade in a raised
position of a preferred embodiment of the invention.

[0031] FIG. 9 is a cut away side view of section of a human spine with the
distractor, gate, and saw in place between the vertebrae.

[0032] FIG. 10 is an exploded isometric view of the implant of a preferred
embodiment of the invention.

[0033] FIG. 11 is an isometric view of the implant of a preferred
embodiment of the invention.

[0034] FIG. 12 is an isometric view of the implant in an extended position
of a preferred embodiment of the invention.

[0035] FIG. 13a is an end view of the inserter of a preferred embodiment
of the invention.

[0036] FIG. 13b is an isometric view of the inserter of a preferred
embodiment of the invention.

[0037] FIG. 14 is a partial isometric view of the inserter and the implant
of a preferred embodiment of the invention prior to attachment.

[0038] FIG. 15 is an isometric view of a guide block of a preferred
embodiment of the invention.

[0039] FIG. 16 is a cut away side view of a section of a human spine and
an implant during positioning by an inserter of a preferred embodiment of
the invention.

[0040] FIG. 17 is a cut away side view of a section of a human spine and
an implant in place prior to the alignment of the vertebrae.

[0041] FIG. 18 is an isometric view of a nut of a preferred embodiment of
the invention.

[0042] FIG. 19a is an isometric view of a plate of a preferred embodiment
of the invention.

[0043] FIG. 19b is a cut away side of a plate of a preferred embodiment of
the invention.

[0044]FIG. 20 is a cut away side view of a section of a human spine with
an implant in a retracted position and a nut and a bolt in place.

[0045] FIG. 21 is a cut away side view of a saw in an alternate saw
embodiment.

[0046] FIG. 22a is a cut away side view of the end of saw in an alternate
embodiment of the invention.

[0047] FIG. 22b is an end view of the end of an alternate saw embodiment.

[0048] FIG. 23a is a top view of the top of the chuck of an alternate saw
embodiment.

[0049] FIG. 23b is a partial cut away side view of the chuck of an
alternate saw embodiment.

[0050] FIG. 24a is a side view of an implant in another embodiment of the
invention.

[0051] FIG. 24b is an end view of an implant in another embodiment of the
invention.

[0052] FIG. 25 is an isometric view of an impactor in conjunction with a
distractor of another embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0053] FIG. 1 is an illustration of a lumbar spine in a patient who has
contracted spondylolisthesis. The vertebrae 10 are separated by vertebral
disk 50. As a result of advanced spondylolisthesis, superior vertebra 20
slips forward in relation to the next inferior vertebra 40 and causes
distended disk 70. To repair slippage of the vertebrae, superior vertebra
20 and inferior vertebra 40 are realigned and fused together. To
accomplish this, a portion of distended disk 70 is removed and replaced
with an implant which maintains realignment and supports the spine until
ossification occurs whereby superior vertebra 20 and inferior vertebra 40
are permanently fused.

[0054] In order to assure proper alignment, a magnetic resonance image
("MRI") or plain lateral radiographs are used to observe the supine
position to measure the severity of the spondylolisthesis condition prior
to surgery. The restorative height of the interbody space after partial
removal of distended disk 70 and the necessary amount of re-alignment can
be estimated by review of the MRI or plain lateral radiographs. The
implant size can be determined by the estimates.

[0055] The present invention uses the anterior surgical approach to the
lumbar spine in order to reach the vertebrae that will receive the
implant. The anterior surgical approach to the lumbar spine is understood
in the art and is not discussed in detail here.

[0056] Referring still to FIG. 1, once the lumbar spine is exposed to the
surgeon, superior vertebra 20, inferior vertebra 40, and distended disk
70 are located and identified. A standard marking pin known in the art is
inserted into distended disk 70 at the putative midline and left in
place.

[0057] The implant should be optimally placed at the midline in the
sagital plane. Lateral radiographs or x-rays are utilized to confirm the
appropriate surgical level and anterior-posterior x-ray imaging
demonstrates the midline relative to the marking pin. Once confirmed, the
midline of distended disk 70 is marked on distended disk 70 by use of
generally accepted marking means. The marking pin is then removed.

[0058] Portion of distended disk 70 is removed. Boundaries of generous
rectangular annulatomy are created in distended disk 70 by use of
scalpel. The size of the annulatomy will depend upon the size of the
implant and allows additional space on either side of implant to allow
interbody arthodesis on both sides of implant after implant is deployed.
The width of annulatomy will be in the range of between about 2 cm and
about 5 cm. Portion of distended disk 70 within the boundary of
annulatomy is removed by use of rongeurs and curettes.

[0059] Vertebral endplate preparation is performed in standard fashion as
known in the art while maintaining cortical endplate integrity centrally.
Anterior osteophytes may also be removed from the ventral aspect of the
vertebral bodies during this stage of the surgery.

[0060] In order to gain the appropriate restorative height between
superior vertebra 20 and inferior vertebra 40, sequentially larger
interbody spreaders are impacted into the rectangular annulotomy in
distended disk 70 until optimal height restoration is achieved. Interbody
spreaders are known in the art. When optimal height restoration is
achieved, interbody spreaders are removed and appropriate height
distractor 110 is inserted.

[0061] FIG. 2 illustrates one embodiment of distractor 110. Distractor 110
is made of titanium, stainless steel, or other commercially available
material which is easily sterilized. Rigid plastics can be used such as
polyvinyl chloride (PVC) in disposable embodiments. Distractor 110 is
rectangular in cross-section and includes hollow distractor channel 115.
Distractor channel 115 is rectangular in cross-section and runs the
length of distractor 110. The dimensions of distractor 110 vary depending
on the optimal height restoration to be achieved, but height of
distractor 110 should generally range between about 0.5 cm and about 1.5
cm and the width of distractor 110 should range between about 2 cm and
about 5 cm. The length of distractor 110 is between about 30 cm and about
60 cm. The thickness of walls of distractor 110 should range between
about 1 mm and about 5 mm depending on the material of construction to
achieve a rigid structure. The dimensions of distractor channel 115
should range between about 0.4 cm and about 1.4 cm high, about 1.9 cm and
about 4.9 cm wide.

[0062] Posterior end of distractor 110 contains distractor arm 117 and
distractor arm 118. Distractor arm 117 extends longitudinally from side
80 of distractor 110. Distractor arm 117 includes distractor point guide
246 having angled surfaces 253 and 254. Opposing angled surfaces 253 and
254 is distractor stop 119. Distractor arm 118 extends longitudinally
from the side 81 of distractor 110 and includes distractor point guide
256 having rounded surfaces 258 and 255. Opposing rounded surfaces 258
and 255 is distractor stop 122. The height of distractor arm 117 and
distractor arm 118 are approximately the same as the height of distractor
110. The width of distractor arm 117 and distractor arm 118 are between
about 0.5 mm and about 1 mm. The width of the distractor arms should
provide rigidity with respect to the body of the distractor. Distractor
arm 118 and distractor arm 117 form implant hollow 130. End gap 120 is
formed at the forward end of implant hollow 130. The preferred design of
end gap 120 is between about 1.7 cm and about 4.7 cm. Distractor stop 122
and distractor stop 119 are between about 0.5 mm and about 2 mm in
length.

[0063] Torque handle 235 is rigidly mounted to distractor body 99. Torque
handle 235 is generally in the range of about 2 cm to about 5 cm in
length with a diameter in the range of about 0.5 cm to about 2 cm. The
preferred location of torque handle 235 is approximately between 1/4 to
1/2 from the anterior end 111 of distractor 110. A set of distractor
graticules 135 are etched at 1 mm intervals on the side of distractor 110
along the outside of distractor arm 118 and distractor arm 117.

[0064] In the preferred embodiment, the cross-sectional height and width
of distractor 110 may vary. In its preferred use, a set of variable
height distractors is provided so that the distractor height which
matches the vertical distance between the vertebrae may be used during
surgery. The preferred set of heights preferably varies in one millimeter
increments between about 5 mm and about 2 cm.

[0065] FIG. 3a illustrates the preferred embodiment of impactor 140.
Impactor 140 includes impactor handle 170 which is cylindrical with a
diameter in the range of about 0.3 cm and about 2 cm. The length of
impactor handle 170 ranges between about 5 cm and about 25 cm. In one
embodiment, impactor handle 170 is etched with impactor centerline 165
across its diameter. Impactor centerline 165 is parallel to the long
cross-sectional axis of impactor body 160.

[0066] Impactor body 160 is formed integrally with impactor handle 170.
Impactor body 160 is rectangular in cross-section and sized to fit within
distractor channel 115 without excessive play. In the preferred
embodiment, the impactor body is sized to allow for approximately 0.3 mm
play between the exterior of the impactor body and the distractor
channel.

[0067] Angled section 141 extends from impactor handle 170 to impactor
body 160 at an angle between about 25 and about 65 degrees. Angled
section 141 serves to center the impactor handle with respect to the
impactor body and distribute impact loads from the impactor handle to the
impactor body as will be further described. The preferred length of
impactor body 160 should range between about 30 cm and about 45 cm. The
posterior end of impactor body 160 includes impactor seat 150 integrally
formed with impactor body 160. Impactor seat 150 is sized and shaped to
fit within end gap 120 shown in FIG. 2. Impactor seat 150 has rounded
surface 155. On either side of impactor seat 150 are stop surface 152 and
stop surface 153. Impactor 140 is preferably made from titanium,
stainless steel, or other materials which are readily sterilized or from
a rigid plastic such as PVC which may be disposed of after use.

[0068] Other cross-sectional shapes of the impactor and distractor are
also acceptable, such as elliptical, as long as the impactor fits inside
the distractor channel such that it can move longitudinally in distractor
channel 115 without rotation and without significant "play" or angular
displacement.

[0069] In use, impactor 140 is placed inside distractor channel 115, such
that impactor seat 150 fits into end gap 120 as shown in FIG. 3b.
Impactor centerline 165 is aligned with the anatomical midline marked
previously. Distractor 110 and impactor 140 are aligned with the
anatomical midline and inserted into the rectangular annulatomy in
distended disk 70. A mallet is used to tap impactor 140 and distractor
110 into the midline sagital plane under fluoroscopic guidance until
posterior edge of distractor 110 reaches the dorsal epiphyseal ring on
the ventrally superior vertebra 20. Impactor 140 is then withdrawn from
distractor channel 115 and distractor 110 is left in situ.

[0070] In the preferred embodiment, impactor 140 is also provided in a set
of variable sizes to match the set of variable sizes of distractor 110,
as previously described.

[0071] FIG. 4 shows distractor 110 in situ between superior vertebra 20
and inferior vertebra 40. Distractor 110 is between superior vertebra 20
and inferior vertebra 40. Once in position, distractor graticules 135 are
used to gauge the amount of slip existing between superior vertebra 20
and inferior vertebra 40.

[0072] FIGS. 5a, 5b and 5c illustrate an embodiment of gate 180. Gate 180
has a gate body 223 bordered by side wall 271, bottom side 269, side wall
284 and top side 268. The gate body also includes saw end 249 and
distractor end 251. In the preferred embodiment, gate 180 has a length of
between about 5 cm and about 10 cm, a width of between about 2.2 cm and
5.8 cm and a height of between about 0.7 cm and about 2.9 cm.

[0073] Gate 180 is provided with saw guide 220 and saw guide 230. Saw
guides 220 and 230 are a pair of slots which are situated approximately
the center of top side 268 to the center of side wall 284, encompassing
approximately 1/4 of the perimeter of gate body 223. The pair of saw
guides are in parallel planes. Saw guide 220 and saw guide 230 terminate
in handle guide 257. Handle guide 257 forms a slot generally in the
center of side wall 284. Handle guide 257 is provided with handle stop
252. The width of saw guides 220 and 230 and handle guide 257 in the
preferred embodiment is between about 0.5 cm and 1.5 cm.

[0074] Gate body 223 is also provided with saw guide 200 and saw guide
210. Saw guides 200 and 210 are a matched pair of slots which are
situated approximately the center of bottom side 269 to the center of
side wall 271, encompassing approximately 1/4 of the perimeter of gate
body 223. The pair of saw guides are in parallel planes. Saw guide 200
and saw guide 210 terminate in handle guide 240. Handle guide 240 forms a
slot generally in the center of side wall 271. Handle guide 240 is
provided with handle stop 242. The width of saw guide 200, saw guide 210
and handle guide 240 in preferred embodiment is between about 0.5 cm and
about 1.5 cm.

[0075] Saw guide 220, saw guide 230 and handle guide 257 are ductedly
connected. Saw guide 220 and saw guide 230 are on centers of between
about 0.5 cm to 3.5 cm in the preferred embodiment. Further, saw guide
220 is approximately 0.9 cm from saw end 249.

[0076] Saw guide 210, saw guide 200 and handle guide 240 are ductedly
connected. Saw guide 210 and saw guide 200 are on centers of between
about 0.5 cm to 3.5 cm in the preferred embodiment. Further, saw guide
210 is approximately 1.9 cm from saw end 249.

[0077] Gate body 223 is further provided with interior channel 195 which
is longitudinally centered within gate body 223. Interior channel 195
includes saw entrance 247. Saw entrance 247 in the preferred embodiment
has dimensions slightly larger than guide body 310 which will be
described in more detail with respect to FIG. 6. The diameter of saw
entrance 247 is maintained by interior channel 195 from saw entrance 247
until gate lip 185. At gate lip 185, interior channel 195 increases in
height and width to accommodate the exterior of distractor 110. The
dimensions of interior channel 195 remain constant from gate lip 185 to
distractor end 251 terminating in distractor entrance 248.

[0078] In one embodiment, gate 180 can also include raised indicator arrow
245 or other visual aid or tactile indicator to indicate which end of
gate 180 is to be inserted over distractor 110.

[0079] In the preferred embodiment, many gates are provided in a kit
during surgery. The gates each have saw guides that are spaced apart at
different lengths with respect to the top and the bottom of each gate.
The different spacings correspond to different distances that the
vertebrae have slipped. In one preferred embodiment, in the less severe
cases, saw guides 230 and 220 will be offset from saw guides 200 and 210
by about 1 mm. The offset between saw guides 230 and 220 and saw guides
200 and 210 will increase by 2 mm increments. In more severe cases, the
amount of slip will be more pronounced and the offset can be
approximately 20 mm. Position of saw guides 200 and 210 on gate 180 will
stay constant. The gates also vary in height to match the variable height
of the distractor.

[0081] Saw 250 includes guide body 310. Guide body 310 includes a
rectangular section 311 and an angular section 312. Rectangular section
311 in the preferred embodiment is sized to fit within saw entrance 247
as shown in FIG. 5b and distractor channel 115 shown in FIG. 2. The
rectangular section tolerance must be such that rectangular section 311
slides longitudinally with respect to distractor channel 115 and interior
channel 195 without significant angular play about the longitudinal axis.
In the preferred embodiment, these tolerances are approximately 0.3 mm.
Angular section 312 connects to flat surface 313. Guide body 310 also
includes spindle hole 301 which traverses the longitudinal axis of guide
body 310 and is sized to fit around spindle shaft 273. Spindle hole 301
is sized to allow rotation with respect to spindle shaft 273.

[0084] Saw 250 and all its components are made from titanium, stainless
steel, or other material which is used with surgical tools and equipment.
In the preferred embodiment, rectangular section 311 of saw 250 is
provided in several sizes in a set of several sizes to match the sizes of
the distractor 110, as previously described. Alternatively, a set of
several saws 250 is provided, each having a rectangular section 311 whose
cross-section is sized to match the distractor channel 115 of the set of
distractors 110. In addition, a set of blades may be provided each having
different dimensions to achieve different lumbar dimensions.

[0086] In the preferred embodiment, saw blade 280 is between 0.9 cm and
4.9 cm long with a width of between 1 mm and 5 mm. Saw blade 280 has a
flat bottom and two curved ends 303 and 305. Saw blade 280 includes a
locking hole 285 of approximate diameter and shape as bolt 295. Curved
end 305 includes saw teeth 304 having a height of about 0.5 mm and about
1.5 mm. Saw blade 280 also includes notches 317 and 318. As shown in FIG.
8b, saw blade 280 in its raised position rests adjacent vertical surface
283 which prevents it from rotating counterclockwise. In lowered
position, as shown in FIG. 8a, notch 318 rests adjacent horizontal
surface 282 and prevents rotation of the saw blade clockwise.

[0089] Saw blade 280 is placed in its lowered position. Saw 250 is then
removed from distractor channel 115 through interior channel 195. Saw 250
is then rotated 180 degrees about its axis and rectangular section 311
replaced is in interior channel 195 of gate 180. Saw 250 is further
reinserted into distractor channel 115.

[0100] As can best be seen in FIG. 12, when assembled, upper half 340 and
lower half 330 of implant 320 are engaged in a sliding relationship
provided by the dovetail guides 385 and 386 residing in dovetail slots
395 and 396. As can be seen in FIG. 11, when assembled, upper half 340
and lower half 330 form implant body 346. Radial anchor 264 is aligned
with radial anchor 370. Radial anchor 261 is aligned with radial anchor
371. Furthermore, upper threaded collar 345 and lower threaded collar 355
are aligned and form a cylindrical threaded attachment collar 356.

[0101] In use, set screw 350 can be rotated either counter-clockwise or
clockwise within lower channel 390 and upper channel 380. The set screw
is retained in position by set screw stop 400 and set screw step 392. As
set screw 350 is rotated, threads 351 engage the threads on upper channel
380 and slide upper half 340 with respect to lower half 330. As upper
half 340 and lower half 330 are displaced, radial anchors 264 and 261 are
displaced with respect to radial anchors 370 and 371 along the
longitudinal axis of implant 320.

[0102] Implant 320 in the preferred embodiment is made from titanium,
stainless steel, alloys such as titanium allow, or other materials which
are easily sterilizable. Implant 320 or parts thereof, may also be made
from composite materials such as synthetic bone. Some composites or
synthetic bone products include demineralized bone matrix, collagen,
ceramics, cements, and polymers, such as silicone and some acrylics and
include products such as Vitoss, Cortoss, Rhakoss, Pro Osteon, and
Gu-Bang.

[0103] In the preferred embodiment, implant body 346 is between about 0.5
cm to about 2.5 cm in diameter and between about 2.0 cm and about 4.5 cm
in length. In the preferred embodiment, cylindrical threaded attachment
collar 356 is between about 0.4 to about 2.4 cm in diameter and between
about 0.5 and 2.0 cm in length. In the preferred embodiment, radial
anchors 264, 261, 370 and 371 have a height (as measured from the center
plane of the implant) of between about 0.5 cm and about 3.5 cm with an
aspect ratio of 1/2 to 11/2 between radial anchors 264, 261, 370, and 371
and diameter of implant body 346.

[0104] In the preferred embodiment, upper half 340 includes exactly two
radial anchors and lower half 330 includes exactly two radial anchors.
However, in other embodiments, the upper half and lower half of the
implant may include more or less than two radial anchors. Furthermore,
the upper half and lower half of implant 320 do not necessarily need to
include the same number of radial anchors. In embodiments which include
different numbers of radial anchors, it will be understood by those
skilled in the art that the same number of saw guides must be included on
gate 180 in order to correspond with the number and orientation of the
radial anchors.

[0106] Lower half 450 includes lower hexagonal section 451 and lower
cylindrical section 453. Lower cylindrical section 453 includes lower
dovetail channel 452. Upper dovetail guide 454 fits within lower dovetail
channel 452 and allows for sliding movement between upper half 440 and
lower half 450. As can best be seen in FIG. 13b, when upper half 440 and
lower half 450 are assembled, inserter 430 assumes an outer circular
perimeter. In the preferred embodiment, this outer circular perimeter is
sized to fit within distractor channel 115, shown in FIG. 2, with
sufficient clearance to allow for rotation of inserter 430. Further, in
the preferred embodiment, the hexagonal shape of upper half 440 and lower
half 450 and inserter 430 is sized to allow for rotation with a tool such
as a spanner wrench. In the preferred embodiment, the length of inserter
430 is sufficient to span the length of distractor body 99.

[0108] Referring to FIG. 15, guide block 460 will be described. Guide
block 460 includes guide block bottom 465 and guide block top 475. Guide
block 460 also includes guide hole 470 which is centrally located within
the guide block and spans its length. Guide block bottom 465 is sized to
fit within distractor channel 115. Guide block top 475 is sized so that
it will not fit within distractor channel 115 but rather abut anterior
end 111 of distractor body 99 (as shown in FIG. 2).

[0109] In use, inserter 430 is used to place the implant in position
between the affected vertebra and rotated into position. More
particularly then to implant the implant, the amount of offset calculated
according to the radiograph is reduced to a number of millimeters. The
implant is adjusted using upper adjustment index marks 360 and lower
adjustment index marks 361 to an offset position using set screw 350. The
amount of offset can be observed by observing the offset between index
marks 360 and 361. In an alternate embodiment, the offset can be derived
by calculating the number of rotations of the set screw and multiplying
by the pitch of the threads. In an alternate embodiment, the pitch of the
threads is set to a convenient number so that a single rotation of the
set screw results in a predetermined movement of the upper and lower
halves, such as 1 mm for example. An example of an offset position is
shown in FIG. 12.

[0110] In use, inserter 430 is assembled and its cylindrical section is
guided into and through guide hole 470 until guide block top 475 reaches
the hexagonal section of the inserter.

[0112] Referring now to FIG. 16, the process of inserting implant 320 into
the affected vertebra will be described. As previously described,
distractor 110 is in position between superior vertebra 20 and inferior
vertebra 40. Implant 320, while attached to inserter 430 is oriented and
placed within distractor channel 115. Implant 320 is placed in distractor
channel 115 with radial anchors 264 and 261, 370 and 371 positioned so
that clockwise rotation of the implant will result in radial anchor 264
and 261 encountering superior vertebra 20 and radial anchor 370 and 371
encounter inferior vertebra 40. Using the hexagonal section of inserter
430, implant 320 is advanced within distractor channel 115 a sufficient
distance to allow guide block bottom 465 to be inserted into distractor
channel 115. Guide block bottom 465 is advanced within distractor channel
115 until guide block top abuts anterior end 111 of distractor body 99.

[0113] Implant 320 is then advanced within distractor channel 115 until
the hexagonal section of inserter 430 abuts guide block top 475.

[0114] The dimensions of guide block top 475 and cylindrical section of
inserter 430 are such that when the hexagonal section of the inserter
abuts guide block top 475, implant 320 is in proper position in relation
to slots 900, 902, 903 and 904 such that radial anchor 264 is adjacent
slot 900, radial anchor 261 is adjacent slot 902, radial anchor 370 is
adjacent slot 904 and radial anchor 371 is adjacent slot 903.

[0115] Inserter 430 is then rotated 90 degrees clockwise such that the
radial anchors are rotated into position in the slots in their respective
vertebrae.

[0116] Once in position, implant 320 is released from inserter 430.

[0117] The diameter of inserter guide hole 470 should provide sufficient
clearance for rotation and transition of cylindrical portion of inserter
430 without excessive play. In the preferred embodiment, the diameter of
guide hole 470 should not exceed the diameter of the cylindrical section
of inserter 430 by more than 0.1 mm.

[0119] Distractor 110 is then removed from between superior vertebra 20
and inferior vertebra 40 by pulling anteriorly.

[0120] FIG. 17 illustrates the positioning of implant 320 between superior
vertebra 20 and inferior vertebra 40 after distractor 110 has been
removed. Upper half 340 is adjacent superior vertebra 20, radial anchor
264 is located in slot 900, radial anchor 261 is located in slot 902.
Lower half 330 is adjacent inferior vertebra 40 and radial anchor 370 is
located in slot 904. Radial anchor 371 is located in slot 903.

[0121] In order to align superior vertebra 20 and inferior vertebra 40,
upper half 340 and lower half 330 are aligned. A spanner is inserted into
spanner slot 405 of implant 320. Set screw 350 is rotated to move lower
implant half 330 anteriorly and upper implant half 340 posteriorally. In
one embodiment, for each complete 360 degrees turn of the set screw will
move lower half 330 1 mm with respect to upper when alignment of the
implant halves is complete, the threads in upper threaded collar 345 and
in lower threaded collar 355 will align. Ideally, alignment of the
implant halves will align the vertebrae.

[0122] After alignment of the vertebrae, an interbody arthrodesis is
performed on each side of implant 320 and between remaining distended
disk 70. The technique for interbody arthrodesis is surgeon's choice from
those known techniques.

[0123] FIGS. 19a and 19b illustrates one embodiment of plate 540. Plate
540 is selected based on shape and size of individual patient's
vertebrae. In one embodiment, the height of plate 540 is between 2.5 cm
and 7 cm and the width of plate 540 is between 1.5 cm and 5 cm. Depth of
plate 540 is between 0.2 cm and 1.5 cm. Plate 540 is slightly concave to
approximate the curvature of inferior vertebra 40 and superior vertebra
20.

[0124] Plate 540 includes plate nut hole 560 in its approximate center.
The diameter of plate nut hole 560 on the anterior side of plate 540 is
between 0.65 cm and 3.4 cm while the diameter of plate nut hole 560 on
the posterior side of plate 540 is between 0.45 cm and 2.5 cm.

[0125] Plate 540 also includes four holes 550. Each hole 550 should have
diameter between about 1 mm and about 9 mm. But these diameters can vary.
The plate is secured to the vertebra by stainless steel screws as known
in the art.

[0126] Preferably, plate 540 should be made of titanium or stainless
steel.

[0127] FIG. 18 illustrates one embodiment of nut 500. Nut 500 has nut head
520 which is elliptical. Diameter of nut head 520 is between 0.65 cm and
3.4 cm preferably. Nut head 520 contains spanner holes 535. Nut body 510
has diameter of between 0.5 cm and 2.5 cm. The diameter of nut body 510
should be approximately the same as diameter of implant body 346. The
length of nut body 510 is between 0.2 cm and 6 cm. Nut 500 should be
construction of titanium or stainless steel. Other rigid materials can be
used. Nut body 510 includes threaded hole 526. Threaded hole 526 is
threaded to match the threads of upper threaded collar 345 and lower
threaded collar 355 on implant 320.

[0129] Plate 540 is then properly aligned with the shape of superior
vertebra 20 and inferior vertebra 40. Corticocancellous screws 570 are
placed into each of the plate screw holes 550 and screwed into the
respective vertebrae by traditional techniques within the field. The
difference in diameters between plate nut hole 560 from front to back
allows articulation of the bolt with respect to the plate. Once plate 540
is attached to superior vertebrae 20 and inferior vertebrae 40 with
screws 570, and is secured via nut 500 to implant 320 the device acts as
a monolithic structure preventing rotational, lateral or
anterior/posterior movement of vertebral bodies 20 and 40 with respect to
each other, allowing ossification of said vertebral bodies.

[0130] Surgery is completed by standard anterior approach surgery
techniques and implant is in place.

[0131] In the event that adjustments need to be made to implant 320,
screws 570, nut 500 and plate 540 can be removed and set screw 350
adjusted with any appropriate spanner head wrench. Nut 500, plate 540 and
screws 570 are then replaced.

[0132] FIGS. 21, 22a and 22b illustrate another preferred embodiment of
the saw. FIG. 21 shows saw 802 with mill bit 750. Saw 802 includes handle
817 and conical section 814. Interior of handle 817 includes motor 860.
Motor 860 is attached to mounting frame 808. Motor 860 is connected to
transmission shaft 700. Switch 840 is integrated into handle 817 and is
connected to motor 860 through wire 850. Switch 840 activates and
deactivates motor 860. Motor 860 is connected to power source such as a
rechargeable lithium ion battery or another renewable power supply as
known in the art.

[0133] Motor 860 rotates transmission shaft 700 between 15,000 to 20,000
rpm. In another preferred embodiment, motor 860 has variable speeds and
speed of motor 860 is modulated through use of switch 840.

[0140] FIGS. 23a and 23b are further illustrations of chuck 660. Bevel
gear 610 is integrally connected to bearing shaft 620. Bearing shaft 620
is integrally connected to jaws 650. Jaws 650 are approximately
cylindrical in shape with mill bit hole 882 removed which is same shape
as end of mill bit 750. Jaws 650 have set screw hole 640. Set screw hole
640 is threaded to mate with set screw 630.

[0141] In one embodiment, mill bit hole 882 has flat surface 642 and
semicircular surface 641. Set screw hole 640 is centered along the
latitudinal axis of flat surface 642.

[0143] Referring now to FIG. 22b, guide body 795 includes horizontal stop
780 and vertical stop 790. Horizontal stop 780 extends from top 782 of
guide body 795 and has horizontal surface 787. Vertical stop 790 is
aligned with bottom 783 of guide body 795. Vertical stop 790 and
horizontal stop 780 cooperate with bit stop 836 to limit the rotation of
the transmission housing and the mill bit to 90 degrees between a
vertical position and a horizontal position.

[0145] In use, mill bit 750 is inserted into mill bit hole 882. Set screw
630 is advanced through set screw hole 770, into set screw hole 640 until
abuts mill bit 750. Saw 802 is then inserted into a distractor as
described in previous embodiment. Switch 840 activates motor 860 by
connecting it to a power source, which rotates transmission shaft 700 and
bevel gear 735. Rotation of bevel gear 735 rotates bevel gear 610 and
chuck 660, which causes mill bit 750 to rotate. Handle 817 is manually
rotated counterclockwise around the longitudinal axis of guide body 795
which rotates mill bit 750 in relation to the longitudinal axis of guide
body 795 and exposing mill bit 750 to vertebrae in order to cut a slot in
the vertebra. After a slot has been cut, handle 817 is manually rotated
clockwise around the longitudinal axis of guide body 795 until mill bit
750 is substantially parallel to latitudinal axis of guide body 795.
Switch 840 then deactivates motor 860. The procedure is repeated for
cutting additional slots in vertebra as previously described with manual
saw embodiment.

[0146] Mill bit 750 has a diameter of between approximately 1 mm and 5 mm
and a length of between 0.6 cm and 3.9 cm and corresponds to the size of
the radial anchors of the implant being inserted between vertebra.
Multiple size mill bits are included and the appropriate size is inserted
to correspond to size needed for the particular implant.

[0147] In some spondylolisthesis conditions, the relocation of vertebra
may either be minor or unnecessary, however the natural tilt and location
between two adjacent vertebrae needs to be maintained and stabilized. For
this type of condition, another embodiment of an implant and
instrumentation are used which includes a tapering to match the tilt of
the vertebrae.

[0148] FIGS. 24a and 24b are illustrative of an additional preferred
embodiment of a tapered implant. Implant 845 has an implant body 853 that
is tapered creating a frustroconical shape. Implant body 853 has implant
body front end 870 and back end 861. The cross-section of front end 870
is circular. The cross-section of back end 861 is circular. Degree of
tapering 875 is the degree by which the tapering occurs along implant
body 853 and ranges between approximately 2 and 10 degrees.

[0150] Implant body 853 has radial anchors 876 and 877 on upper half 862
and radial anchors 878 and 879 on lower half 864. Radial anchors 876,
877, 878, and 879 are substantially perpendicular to implant seam 855.
Radial anchors 878 and 876 have less surface area than radial anchors 877
and 879, and are reduced in area to conform to a modified distractor as
shown in FIG. 25. Other features of implant 845 are similar to those
previously described in other embodiment.

[0151] FIG. 25 is illustrative of other preferred embodiments for a
distractor and impactor to be used with tapered implant 845. FIG. 25
illustrates impactor 950 within distractor 940.

[0152] Distractor 940 has distractor arm 895 and distractor arm 892.
Distractor arm 895 extends longitudinally from side 955 of distractor
940. Distractor arm 892 extends longitudinally from side 945 of
distractor 940. Distractor arm 895 has taper arm 890 which tapers both
the top and bottom between an approximate 2 and 10 degree angle along the
longitudinal axis of distractor arm 895. Taper arm 897 on distractor arm
892 tapers the height from both the top and the bottom between an
approximate 2 and 10 degree angle. Taper arm 897 includes distractor stop
910 and taper arm 890 has distractor stop 906. The remaining features of
distractor 940 are consistent with previously disclosed embodiment of
distractor.

[0153] Impactor 950 has impactor head 911. The posterior end of impactor
head 911 has tapered end 898. Tapered end 898 has between approximately 2
and 10 degrees of taper along the longitudinal axis of impactor head 911.
Tapered end 898 ends in impactor seat 920 and on either side of impactor
seat 920 are stop surfaces 930 and 931. The tapering of tapered end 898
corresponds to the tapering of taper arm 890 and taper arm 897 such that
stop surfaces 930 and 931, when fully inserted, touch distractor stop 906
and distractor stop 910 and do not extend beyond edges of distractor arms
892 or 895. The remaining features of impactor 950 are consistent with
previously disclosed embodiment of impactor.

[0154] As disclosed with prior embodiments, with the tapered implant
system, the implant, distractor, impactor, and other parts necessary to
complete the disclosed surgery have a variety of heights depending on the
patient and the condition to be resolved.